Mammals are more recently derived amniotic chordates, with fur and mammary glands

The common display of chimp to man is deeply problematic

Common Misconceptions of human evolution



  • Our ancestors were chimpanzees: WRONG!
    • RIGHT: We share a common ancestor with chimps


  • Human evolution = series of steps from ancestor to Homo sapiens: WRONG!
    • RIGHT: Human evolution is more like bush than a ladder
    • Homo sapiens is a branch on a bushy phylogenetic tree


  • Human characteristics like upright posture and large brain evolved together: WRONG!
    • RIGHT: Early ancestry included upright walkers with small brains

Primate phylogeny (Misconception #1)

The big picture: Humans are evolutionary newcomers

  • Our closest living relatives are the chimpanzees
    • common ancestor with chimps ~ 6-7mya
    • genomes are 98-99% similar to chimps
    • 1% difference means a lot!!
      • 19 regulatory genes differ
      • 600 genes differ in protein expression


  • Hominin derived characters:
    • bipedal
    • large brain…
    • reduce jawbone and jaw muscles
    • shorter digestive tract


  • These characters are not unique to Homo sapiens!

Hominins: part of primate family that includes genus Homo


  • ~20 species described (fossils) in the tribe
    • at least 3 different genera (e.g., Homo)
    • brain size, teeth shape, body size
    • inferred tool use/culture/language
    • species had different combos of each


  • Really old fossils
    • Sahelantrophus tchadensis (Toumai): 6.5mya
      • fossil connection to hominins missing
    • Ardipithecus ramidus (Ardi): 4.4 mya
      • lived in trees & on ground


  • We (Homo sapiens) are the sole surviving taxon

Hominin evolution was not a linear process

Hominin evolution:
brain volume increases over macroevolutionary events

Hominin evolution: The jaw (form and function)

Why did we evolve to walk on 2 legs? (form and function)

The earliest Hominins evolved in Africa


  • All but the 4 most recent species were found only on the African continent


  • Oldest hominin fossil found in Chad
    • ~6-7 mya, found in 2001
    • diverged from common ancestor with chimps (~7mya)


  • Hominin diversity increased ~4-2 mya
    • Australopithecus genus
    • ‘Lucy’ fossil in Ethiopia
      • more diverse diet
    • definitely bipedal
    • gorilla-like shoulders: climbers
    • possible tool use

Lucy (Australopithecus afirensis) direct ancestor of Homo?

Homo genus in the fossil record


  • Early Homo genus is composed of modern humans
    • all species are called humans
    • ~2mya to present day


  • 8-10 species described!
    • flat and narrow faces
    • small jaws and teeth
    • larger brain cases


  • Tool-making was their hallmark

Brain volume in Homo species increased disproportionately

Species of Hominins and Homo overlapped!

Homo species left Africa (H.ergaster then H.erectus)

Homo sapiens evolution

  • Evolved on the African continent


  • Descended from a 2nd wave of immigration out of Africa
    • ‘Out of Africa’ hypothesis
    • ~100,000 ya
    • fossil and DNA evidence shows migration
    • not the first species to leave


  • 1 population left Africa, then split into 3 groups
    • ~2,000 generations ago


  • Natural selection for the ability to reason and communicate
    • Increased tool use and language
    • resulted in larger brains

H.neandertalensis and H.sapiens interacted!


  • Neanderthals evolved in Eurasia
    • split from a common ancestor ~ 500,000 ya
    • buried dead
    • used art


  • Co-existed with H.sapiens until ~ 30,000 years ago
    • Middle East and Europe


  • Only one lineage survived
    • natural selection?
    • out competed?
    • extirpation of Neanderthals by modern humans?

H.neandertalensis and H.sapiens interbred!

Recent findings: new modern species?




  • Really small new species (H.floresiensis)?
    • fossils in Indonesian island cave
    • allegedly 13,000 years old


  • Archaeologists seeking path to Australia


  • Controversy: diseased H.sapiens?

Where is Human evolution heading?

Newish Traits = Cooler body temperatures, less hair, smaller jaws and teeth

Regional populations adaptions = surface area:volume by climate (regional), nose and lips shapes by climate, strait hair in cool climates, eye lid folds in Asian populations to protect eye from UV, thicker fat in artic populations, large brain volumes in cold, climates, reemergence of lactase, skin color and vitamin D synthesis by region, resistance to malaria, increased susceptibility to allergies/asthma